1. Technical Field
The present invention relates to an imaging apparatus and a live-view image display method thereof.
2. Description of the Related Art
An imaging apparatus, such as a digital camera, has a function of displaying a so-called live-view image on a monitor by repeating a series of operations including a shooting process, generation of display image data, and display of an image based on the generated display image data on a monitor, when a shooting mode which is used to perform shooting is set. Then, a user can shoot while checking framing or a shooting state using the displayed live-view image.
Also, the imaging apparatus has a function of shooting while changing image processing parameters such as a white balance, chroma, and tone. For example, it is possible to set various modes (hereinafter, referred to as “image processing modes”) which are different in image processing even if they are the same in shooting condition, such as exposure. Examples of the various image processing modes include (i) a standard mode in which a subject is expressed with red (R), green (G), and blue (B) colors, (ii) a sepia mode in which a subject is reproduced in sepia, (iii) a monochrome mode in which a subject is expressed with black and white colors, and (iv) a film mode in which a subject can be expressed as if the subject is shot with a particular silver halide film.
Thus, since many image processing modes can be set, a user may wonder which image processing mode is suitable for a scene. For this reason, JP 2008-211843 A and JP 2007-274581 A have proposed the following imaging apparatuses. That is, imaging apparatuses perform plural different image processings for image data acquired by shooting and perform multi-screen display of a plurality of live-view images, which have been subjected to the different image processing, respectively, on a monitor. In these imaging apparatuses, it is possible to compare the images obtained through the different image processing with each other. Accordingly, it becomes easy to select an image processing mode suitable for the scene.
FIG. 13 is a view showing an example of the configuration of an imaging apparatus and an example of a timing charge for image generation. In this imaging apparatus, dot-sequential imaging signals (RAW data) which are acquired from an imaging sensor by shooting under control of a shooting control section are recorded in a memory such as an SDRAM, image processing is sequentially performed for the RAW data plural times (in this example, twice) while changing image processing parameters, screen data is generated by mixing image data (an image 1 and an image 2) which are acquired by the image processing, and then two live-view images are displayed on a monitor by displaying a screen based on the screen data on the monitor.
In the configurations shown in FIG. 13, JP 2008-211843 A and JP 2007-274581 A, it is necessary to perform the image processing for the RAW data twice in order to display one screen. Accordingly, if the configurations are compared with a general configuration in which only one live-view image is displayed, an amount of image processing simply doubles. Increase in amount of image processing is proportional to the number of live-view images displayed on a monitor. Accordingly, in order to display three or four live-view images, the amount of image processing increases to be three or four times as large as that in the general configuration. As a result, the power consumption increases with increase in amount of image processing. Particularly, if the size of RAW data becomes large due to increase in number of pixels of the imaging sensor, there is a concern that the power consumption will further increase. Also, as the number of pixels increases, the driving frequency of the imaging sensor also increases. As a result, the power consumption further increases. For this reason, if a function of displaying a plurality of live-view images is provided, increase in power consumption becomes more noticeable.
As another method of displaying a plurality of live-view images, FIG. 14 shows a method in which a plurality of live-view image processing sections are provided which generate the display image data by pipeline processing, and plural image processings are simultaneously performed for the RAW data. In this method, however, there is a concern that cost, power consumption, and an apparatus size will increase because the plurality of live-view image processing sections are provided.
Moreover, as further another example of displaying a plurality of live-view images, FIG. 15 shows a method in which one live-view image processing section is provided and an image 1 and an image 2 are generated alternately for every frame while changing the image processing for every frame in the live-view image processing section. In this method, there is no concern that cost, power consumption, and an apparatus size will increase because one live-view image processing section is provided. However, the image 1 and the image 2 are different in shooting timing. Accordingly, if there is a moving subject, the subject in the image 1 and the subject in the image 2 would be shot at different timings. For this reason, it is difficult to accurately compare the image 1 with the image 2. Also, since both the image 1 and the image 2 are displayed as images which are thinned out by one frame, a frame rate of each of the two live-view images is reduced, which makes it difficult to smoothly display images.